1. Field of the Invention
The invention relates to a control head assembly that automatically locks a control lever thereof into one of two or more selected positions.
2. Prior Art
Manually operated control heads have been used for many years on marine vessels and on other vehicles and apparatus requiring actuation of cables, control rods, pneumatic or hydraulic valves, etc. Previous control heads commonly have several positions and means are often provided to locate the control lever in a particular position that resists a tendancy of the lever to shift from that position due to vibration, accidental knocking or other situations causing creep of the lever with resulting loss of the desired control setting.
Some of these devices have levers which are indexed by movable detents which engage recesses to locate the lever in a desired setting. The indexing means sometimes require manual actuation to disengage the detent from the recess before shifting the lever, which in some devices, requires two handed operation. Two handed operation is inconvenient at times when the other hand is occupied and is not free to disengage the indexing means. Other lever indexing means include a spring-loaded detent which resiliently engages a complementary recess. These spring-loaded types do not actually require two handed actuation, but the levers of such devices are prone to creep due to vibration and/or accidental knocking.
In marine applications, where several selected positions are commonly required, the control lever is commonly made to have an exaggerated flexibility within one plane, and yet to be relatively stiff in a mutually perpendicular plane. A gate means fixed to the control head body is provided with a series of steps or recesses representing control positions which can be selectively engaged by the operator bending the lever in the plane of greater flexibility to disengage a step so as to permit rotation of the lever within the plane having greater stiffness. Devices of this general type are shown in U.S. Pat. Nos. 3,350,957 issued to Morse and 3,287,991 issued to Eckert. Whilst this type of control lever is excellent in many applications, it is not unusual for the lever to be accidentally pushed out of a selected position because commonly the lever is biased by its resilience in such a manner that it can slide off the step under a relatively low force and thus is prone to accidental disengagement which can result in accidents.
U.S. Pat. Nos. 3,048,675 and 3,525,272 both issued to Olson, disclose control heads with relatively stiff levers which are shiftable between series of oppositely facing pins that form mazes through which the levers move to selected positions. Such levers are hinged on rotatable shafts which also permit some rocking of the levers to negotiate the mazes. Whilst these levers are less prone to accidental shifting, the control heads are relatively complex and can be costly to purchase and service. Furthermore, they are usually for applications that require following a step-by-step sequence of operations and thus are not suitable where it might be desirable to avoid using intermediate positions.
Furthermore, many of the prior art multi-position control levers are awkward to use in very cold environments which require operation of the controls with heavily gloved hands. Where operation of the lever requires intricate manipulation due to the relatively complex indexing means, heavily gloved hands increase the difficulty of selecting a particular control position.